java.util.stream

Class Collectors

java.lang.Object

java.util.stream.Collectors

public final class Collectors
extends Object

See the official Java API doc for details.

Method Summary

Modifier and Type	Method and Description
static <T> Collector<T,?,Double>	averagingDouble(ToDoubleFunction<? super T> mapper)
static <T> Collector<T,?,Double>	averagingInt(ToIntFunction<? super T> mapper)
static <T> Collector<T,?,Double>	averagingLong(ToLongFunction<? super T> mapper)
static <T,A,R,RR> Collector<T,A,RR>	collectingAndThen(Collector<T,A,R> downstream, Function<R,RR> finisher)
static <T> Collector<T,?,Long>	counting()
static <T,K> Collector<T,?,Map<K,List<T>>>	groupingBy(Function<? super T,? extends K> classifier)
static <T,K,A,D> Collector<T,?,Map<K,D>>	groupingBy(Function<? super T,? extends K> classifier, Collector<? super T,A,D> downstream)
static <T,K,D,A,M extends Map<K,D>> Collector<T,?,M>	groupingBy(Function<? super T,? extends K> classifier, Supplier<M> mapFactory, Collector<? super T,A,D> downstream)
static Collector<CharSequence,?,String>	joining()
static Collector<CharSequence,?,String>	joining(CharSequence delimiter)
static Collector<CharSequence,?,String>	joining(CharSequence delimiter, CharSequence prefix, CharSequence suffix)
static <T,U,A,R> Collector<T,?,R>	mapping(Function<? super T,? extends U> mapper, Collector<? super U,A,R> downstream)
static <T> Collector<T,?,Optional<T>>	maxBy(Comparator<? super T> comparator)
static <T> Collector<T,?,Optional<T>>	minBy(Comparator<? super T> comparator)
static <T> Collector<T,?,Map<Boolean,List<T>>>	partitioningBy(Predicate<? super T> predicate)
static <T,D,A> Collector<T,?,Map<Boolean,D>>	partitioningBy(Predicate<? super T> predicate, Collector<? super T,A,D> downstream)
static <T> Collector<T,?,Optional<T>>	reducing(BinaryOperator<T> op)
static <T> Collector<T,?,T>	reducing(T identity, BinaryOperator<T> op)
static <T,U> Collector<T,?,U>	reducing(U identity, Function<? super T,? extends U> mapper, BinaryOperator<U> op)
static <T> Collector<T,?,DoubleSummaryStatistics>	summarizingDouble(ToDoubleFunction<? super T> mapper)
static <T> Collector<T,?,IntSummaryStatistics>	summarizingInt(ToIntFunction<? super T> mapper)
static <T> Collector<T,?,LongSummaryStatistics>	summarizingLong(ToLongFunction<? super T> mapper)
static <T> Collector<T,?,Double>	summingDouble(ToDoubleFunction<? super T> mapper)
static <T> Collector<T,?,Integer>	summingInt(ToIntFunction<? super T> mapper)
static <T> Collector<T,?,Long>	summingLong(ToLongFunction<? super T> mapper)
static <T,C extends Collection<T>> Collector<T,?,C>	toCollection(Supplier<C> collectionFactory)
static <T> Collector<T,?,List<T>>	toList()
static <T,K,U> Collector<T,?,Map<K,U>>	toMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper)
static <T,K,U> Collector<T,?,Map<K,U>>	toMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper, BinaryOperator<U> mergeFunction)
static <T,K,U,M extends Map<K,U>> Collector<T,?,M>	toMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper, BinaryOperator<U> mergeFunction, Supplier<M> mapSupplier)
static <T> Collector<T,?,Set<T>>	toSet()

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, toString

Method Detail

averagingDouble

public static <T> Collector<T,?,Double> averagingDouble(ToDoubleFunction<? super T> mapper)

averagingInt

public static <T> Collector<T,?,Double> averagingInt(ToIntFunction<? super T> mapper)

averagingLong

public static <T> Collector<T,?,Double> averagingLong(ToLongFunction<? super T> mapper)

collectingAndThen

public static <T,A,R,RR> Collector<T,A,RR> collectingAndThen(Collector<T,A,R> downstream,
                                                             Function<R,RR> finisher)

counting

public static <T> Collector<T,?,Long> counting()

groupingBy

public static <T,K> Collector<T,?,Map<K,List<T>>> groupingBy(Function<? super T,? extends K> classifier)

groupingBy

public static <T,K,A,D> Collector<T,?,Map<K,D>> groupingBy(Function<? super T,? extends K> classifier,
                                                           Collector<? super T,A,D> downstream)

groupingBy

public static <T,K,D,A,M extends Map<K,D>> Collector<T,?,M> groupingBy(Function<? super T,? extends K> classifier,
                                                                       Supplier<M> mapFactory,
                                                                       Collector<? super T,A,D> downstream)

joining

public static Collector<CharSequence,?,String> joining()

joining

public static Collector<CharSequence,?,String> joining(CharSequence delimiter)

joining

public static Collector<CharSequence,?,String> joining(CharSequence delimiter,
                                                       CharSequence prefix,
                                                       CharSequence suffix)

mapping

public static <T,U,A,R> Collector<T,?,R> mapping(Function<? super T,? extends U> mapper,
                                                 Collector<? super U,A,R> downstream)

maxBy

public static <T> Collector<T,?,Optional<T>> maxBy(Comparator<? super T> comparator)

minBy

public static <T> Collector<T,?,Optional<T>> minBy(Comparator<? super T> comparator)

partitioningBy

public static <T> Collector<T,?,Map<Boolean,List<T>>> partitioningBy(Predicate<? super T> predicate)

partitioningBy

public static <T,D,A> Collector<T,?,Map<Boolean,D>> partitioningBy(Predicate<? super T> predicate,
                                                                   Collector<? super T,A,D> downstream)

reducing

public static <T> Collector<T,?,Optional<T>> reducing(BinaryOperator<T> op)

reducing

public static <T> Collector<T,?,T> reducing(T identity,
                                            BinaryOperator<T> op)

reducing

public static <T,U> Collector<T,?,U> reducing(U identity,
                                              Function<? super T,? extends U> mapper,
                                              BinaryOperator<U> op)

summarizingDouble

public static <T> Collector<T,?,DoubleSummaryStatistics> summarizingDouble(ToDoubleFunction<? super T> mapper)

summarizingInt

public static <T> Collector<T,?,IntSummaryStatistics> summarizingInt(ToIntFunction<? super T> mapper)

summarizingLong

public static <T> Collector<T,?,LongSummaryStatistics> summarizingLong(ToLongFunction<? super T> mapper)

summingDouble

public static <T> Collector<T,?,Double> summingDouble(ToDoubleFunction<? super T> mapper)

summingInt

public static <T> Collector<T,?,Integer> summingInt(ToIntFunction<? super T> mapper)

summingLong

public static <T> Collector<T,?,Long> summingLong(ToLongFunction<? super T> mapper)

toCollection

public static <T,C extends Collection<T>> Collector<T,?,C> toCollection(Supplier<C> collectionFactory)

toList

public static <T> Collector<T,?,List<T>> toList()

toMap

public static <T,K,U> Collector<T,?,Map<K,U>> toMap(Function<? super T,? extends K> keyMapper,
                                                    Function<? super T,? extends U> valueMapper)

toMap

public static <T,K,U> Collector<T,?,Map<K,U>> toMap(Function<? super T,? extends K> keyMapper,
                                                    Function<? super T,? extends U> valueMapper,
                                                    BinaryOperator<U> mergeFunction)

toMap

public static <T,K,U,M extends Map<K,U>> Collector<T,?,M> toMap(Function<? super T,? extends K> keyMapper,
                                                                Function<? super T,? extends U> valueMapper,
                                                                BinaryOperator<U> mergeFunction,
                                                                Supplier<M> mapSupplier)

toSet

public static <T> Collector<T,?,Set<T>> toSet()